Year of Award

2009

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Environmental Studies

Department or School/College

Environmental Studies Program

Committee Chair

Vicki Watson

Commitee Members

Dan Spencer, Solomon Harrar

Keywords

ecoregion, restoration, stream management, stream temperature, temperature regime, thermal variability

Abstract

Water temperature is a physical property that fundamentally affects stream ecology and is considered an important water quality parameter from scientific and legal view points. On global, catchment and reach scales, anthropogenic activities have substantially altered natural stream temperature regimes, impairing these systems’ ability to maintain ecological integrity. Thermal degradation often can be attributed to a variety of human activities, and global climate change, which has been accelerated by the demands of an exponentially expanding human population, will play a central role in defining stream temperature regimes in the future. Natural spatial and temporal variability in stream temperatures adds to the complexity of regulating thermal pollution and restoring natural conditions of stream ecosystems. As such, managers would benefit from a comprehensive understanding of the thermal dynamics and primary drivers, including air temperature, of the thermal energy budgets in unaltered, or reference, streams. In this study, a random coefficient regression model was developed and used to analyze variability in summer daily average water temperatures and the relationship between summer daily average air and water temperatures of thirty-six of the Montana Department of Environmental Quality’s reference streams. These streams represent four of Montana’s seven Level III ecoregions: Middle Rockies, Northern Rockies, Northwestern Glaciated Plains, and Northwestern Great Plains. Variability in stream temperatures between ecoregions, between streams within ecoregions, and the air-water temperature relationship were primary considerations. This model indicates that there is not significant variability between ecoregions in Montana’s reference stream temperatures and in the air-water temperature relationship. Alternately, the model indicates that there is significant variability between streams within each ecoregion in reference stream temperatures and the air-water temperature relationship. Equations representing the expected daily average water temperatures of reference streams, given values of daily average air temperature with zero and one-day lag, are also presented. Finally, the management implications of this predictive model are discussed, and a holistic approach is recommended for developing thermal regime-based stream temperature standards, which are critical for the restoration and maintenance of ecological integrity, based on ‘natural’ conditions in reference streams.

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© Copyright 2009 Kathryn Elizabeth Makarowski